The invention relates to a device for gassing liquids, in particular for aerating waste water, by means of a gas distributor that can be connected to a gas supply device, that is to be arranged below the liquid level and that has at least one membrane-like wall made of a flexible material with a plurality of gas discharge openings.
Such a device for fine bubble aeration of waste water is known from DE-OS 22 61 994. An air hose that is made of an elastic material, attached at one end to an air supply line and closed at the other end, is provided with a non-perforated bottom side and an upper side provided with a plurality of air discharge openings. The air hose is held at its longitudinal borders by a carrier member, and a membrane, which is under the tension of an air cushion and which is formed defining an air channel attached to the air supply line, is arranged in the air hose. The two hose walls are connected to one another on two longitudinal borders by a welding seam and form a loop which envelops one of two strand-shaped carrier members. The membrane which is under the tension of an air cushion is also welded on its two side borders with the two hose walls. Furthermore, the air hose is braced at its two side borders by a structural steel plate, which covers the welding seams and is supposed to prevent their peeling off. The rigidity and the weight of the air hose is increased by the structural steel plate. It can also be provided on the bottom side of the air hose, the weight being designed preferably somewhat greater than the buoyancy of the hose filled with air. This known aeration device is time consuming to build and, therefore, expensive.
A device for aerating liquids through compressed air pipe systems is known from DE-PS 507 294. In this device, air supply pipes made of perforated metallic or other suitable material are enveloped by rubber sleeves which have fine perforations that do not open until under the pressure of the air fed into the air pipe system. In this manner the possibility of fine aeration and the provision of a valve effect when the air flow is turned off is to be achieved. The rubber sleeves involve a special cost for their support, i.e. of the overall jet pipe system. In addition, the replacement of worn or defective rubber sleeves is very time-consuming.
A special support structure for a membrane is also deemed necessary according to the proposal of DE-PS 34 10 267. In this known gassing device, a foundation, which has at least one inlet for the gas, is provided. The membrane covers the foundation and is fastened thereto. Furthermore, a device to limit the lift of the membrane is fastened to the foundation. The inlet for the gas is guided as the passage opening through the foundation. The lifting device comprises a connection which is fastened at one end thereof to the membrane in the covering region of the passage opening and at another end thereof with a counterpart arranged in the region of the passage opening. Here too, there are many parts to be assembled, a state that makes the gassing device expensive with respect to time and material cost.